Perform IDNA2008 lookup string conversion on domain name src , as described in section 5 of RFC 5891. Note that the input string must be encoded in UTF-8 and be in Unicode NFC form.

Pass IDN2_NFC_INPUT in flags to convert input to NFC form before further processing. Pass IDN2_ALABEL_ROUNDTRIP in flags to convert any input A-labels to U-labels and perform additional testing. Multiple flags may be specified by binary or:ing them together, for example IDN2_NFC_INPUT | IDN2_ALABEL_ROUNDTRIP.